Gelled hydrocarbon fluids have been used for pipeline cleaning, well stimulation, and for cleaning well bores, but the most common and economically important use for gelled fluids in hydrocarbon recovery is in formation fracturing, which is well known. See, for example, Smith et al U.S. Pat. No. 5,417,287, Graham et al U.S. Pat. No. 6,004,908 and U.S. Pat. No. 6,147,034, and Taylor et al U.S. Pat. Nos. 6,511,944, 6,544,934, and U.S. Pat. No. 7,341,103. The gelled liquid is sent down the well under great pressure and through perforations in the well piping, where it causes fractures in the earth formation. The gelled fluid typically will also suspend and transport a hard granular material such as sand, known as a “proppant” for its function of maintaining the openings of the fissures so the recovered oil or gas can be drawn from the formation into the recovery system. The gelled fracturing fluid will typically also carry with it compatible gel breakers, as the operators will not want the gel to impede the flow of indigenous hydrocarbons once the proppants are in place.
Generally, the hydrocarbon gels comprise a hydrocarbon base such as an oil, a phosphate ester or phosphonic acid ester, and an aluminum or iron salt as a crosslinker. In addition to forming a gel by crosslinking, the phosphate ester component functions as a corrosion inhibitor for the tubes, pipes and metal apparatus used in drilling, and the iron compounds can function as sulfide scavengers especially in the presence of oxygen.
While the hydrocarbon base is conventionally kerosene, diesel oil, fuel oils, gas distillates, crude oil, and even esters or olefins, it has not been until recently that liquefied petroleum gas, sometimes known as LPG, has been used for the hydrocarbon base. Commercial LPG commonly contains about 90% propane, but the composition may vary somewhat. LPG is used as the base hydrocarbon, or for mixing with a base hydrocarbon, by Taylor et al in U.S. Pat. No. 7,341,103.
As related in Fordyce et al U.S. patent application Ser. No. 12/345,531, paragraph 0030:                “LPG's tend to produce excellent fracturing fluids. LPG is readily available, cost effective and is easily and safely handled on surface as a liquid under moderate pressure. LPG is completely compatible with formations and formation fluids, is highly soluble in formation hydrocarbons and eliminates phase trapping—resulting in increased well production. LPG may be readily and predictably viscosified to generate a fluid capable of efficient fracture creation and excellent proppant transport. After fracturing, LPG may be recovered very rapidly, allowing savings on cleanup costs.”        
While Fordyce et al say that LPG can be readily and predictably viscosified, they do not describe gel generating compositions for LPG to be used in extreme low temperatures. See also Loree et al U.S. patent application Ser. No. 12/203,072, paragraph 0042:                “ . . . the extremely low surface tension of the LPG eliminates or at least significantly reduces the formation of liquid blocks created by fluid trapping in the pores of the formation. This is contrasted with the high surface tension of water, which makes water less desirable as a conventional fluid. LPG is nearly half the density of water, and generates gas at approximately 272 m(3) gas/m(3) of liquid. LPG comprising butane and propane has a hydrostatic gradient at 5.1 kPa/m, which greatly assists any post-treatment clean-up required, by allowing greater drawdown. This hydrostatic head is approximately half the hydrostatic head of water, indicating that LPG is a naturally under balanced fluid.        
Again, while Loree et al describe apparatus and methods said to overcome the difficulties incident to the incorporation of proppant into LPG fracturing fluids, they do not address the chemistry of gels useful for LPG or propane fracturing fluids in extreme low temperatures—that is, −20° C. or lower.
Workers in the art have had difficulties making functional LPG gels, utilizing prior art gelling methods and ingredients, under very cold conditions at the wellhead where the temperature may be −20° C. or lower. Under such conditions, conventional gel systems react only sluggishly and tend to be too viscous.